Are polymers Hyperelastic?

As well as exhibiting hyperelastic behavior, polymers are prone to manufacturing variability. This manufacturing variability must be considered in the process of selecting hyperelastic model for the analysis of polymers.

Are hyperelastic materials incompressible?

The hyperelastic material is a special case of a Cauchy elastic material. The most common example of this kind of material is rubber, whose stress-strain relationship can be defined as non-linearly elastic, isotropic, incompressible and generally independent of strain rate.

What is a nonlinear elastic material?

Nonlinear elastic materials present nonlinear stress-strain relationships even at infinitesimal strains — as opposed to hyperelastic materials, where stress-strain curves become significantly nonlinear at moderate to large strains.

What is D1 in Mooney Rivlin?

An example of Mooney-Rivlin hyperelastic analysis Here we define the rubber material and input the parameters as: C10 = -0.55 MPa, C01 = 0.7 MPa, C20 = 1.7 MPa, C11 = 2.5 MPa, C02 = -0.9 MPa, D1 = 0.001 MPa^-1.

Is polyethylene an elastomer?

In high-density polyethylene, for example, the long sequences of ethylene units that make up the polymer spontaneously crystallize at temperatures below about 130 °C (265 °F), so that, at normal temperatures, polyethylene is a partially crystalline plastic solid. Polymers that can do so are called elastomers.

Is rubber a linear material?

Some materials have a non-linear relationship between stress and strain, a behavior exhibited by materials such as a rubber. These are nonlinear elastic materials for which the slope of the stress-strain curve, (ds/de)e, is the strain dependent elastic modulus, the Tangent modulus.

What is incompressibility parameter?

This test characterizes the compressibility and volumetric expansion of the material by measuring the change in volume of the test sample due to a change in pressure (or temperature). Therefore; 2 divided by the slope of this line gives the incompressibility parameter “d”.

What is incompressible material?

When a material is incompressible, the volume remains the same or change in volume is zero, when a body undergoes deformation. This gives, J = 1.

Can a material be elastic but not linear?

Both linear and nonlinear elastic materials will elastically return to an “unloaded” state after loading (without permanent deformations), but the relationship between stress and strain is different in them. It’s linear for linear elastic material (hence the name) and more complex in a nonlinear case.

What is nonlinear material?

A nonlinear material model can be defined as nonlinear elastic where the part returns to a zero strain state when the load is removed, or elasto-plastic where permanent strain begins to accumulate after reaching the yield strength of the material.

What is Mooney-Rivlin constants?

Most use Mooney-Rivlin constants to define the material behaviour and these constants are simply related to the rigidity modulus for a given material. The statistical theory for the stress-strain relationship for rubbers implies that the material will obey Hooke’s Law in shear though not in tension or compression.

What is the Mooney-Rivlin equation?

First and Second Constants: The Mooney-Rivlin expression σ = 2(C 1 + C 2/λ)(λ – 1/λ 2) can be manipulated to take the following form: σ / [2(λ – 1/λ 2)] = C 2 + λ -1 + C 1. This is analogous to a linear expression of the form y=mx+b, where…

What is an example of hyperelastic material?

Hyperelastic material. For many materials, linear elastic models do not accurately describe the observed material behaviour. The most common example of this kind of material is rubber, whose stress – strain relationship can be defined as non-linearly elastic, isotropic, incompressible and generally independent of strain rate.

What is the relationship between stress and strain in hyperelastic material?

Stress–strain curves for various hyperelastic material models. A hyperelastic or green elastic material is a type of constitutive model for ideally elastic material for which the stress–strain relationship derives from a strain energy density function. The hyperelastic material is a special case of a Cauchy elastic material.

What is hyperelasticity and why does it matter?

Hyperelasticity provides a means of modeling the stress–strain behavior of such materials. The behavior of unfilled, vulcanized elastomers often conforms closely to the hyperelastic ideal.

What is hyper-elasticity of a material?

Hyper means excessive, so hyper-elasticity means excessively elastic. A normal stress-strain curve tend to show plasticity after the elastic limit. But a Hyper elastic material is elastic even at very high strains.